This invention relates to a self-opening and selfclosing umbrella, particularly to an improved self-opening and self-closing umbrella which overcomes several problems with a conventional self-opening and self-closing umbrella as illustrated in U.S. Pat. No. 4421133. Unless these problems are successfully solved, the umbrella can hardly be expected to serve people satisfactorily at a rainy day.
The first problem with a conventional self-opening and self-closing umbrella is that it cannot open quickly and fully when it is quickly raised up from the ground, against which the umbrella has been pushed for opening. 11 is is because a much stronger elastic strength is required of the spring disposed in the middle tube of the shaft the instant when the folded canopy is made to spread, something like a motor car which needs a greater horsepower to start, and then the elastic force of the spring is much diminished by an air pressure or resistance suddenly exerted on the canopy on the other hand. In most cases, the umbrella will stand half opened.
The second problem with a conventional self-opening and self-closing umbrella is that it cannot always close to a condition as planned wherein it folds tightly for convenient carrying and stands ready for opening again. This is also because of the air pressure or resistance now exerted on the inside of the canopy, especially when there is a wind blowing.
The third problem with a conventional self-opening and self-closing umbrella is that the lower inner tube of the telescoping shaft bends easily at the point where it meets the lower end of the middle tube. This is because of the fact that the inner tube is normally relatively weak in structure and that a sudden strong force is always abnormally exerted on that point when the umbrella is not pushed in a proper or perpendicular manner against the ground for opening, as often so with a new user of the umbrella.
Then still another problem with a conventional selfopening and self-closing umbrella is that its handle portion is not fixed with respect to its shaft. The umbrella cannot, therefore, be used as a walking stick.